Creation of the first room

We will start with learning how to create a brush and after this how to create a whole room. So let's get started:
Select the top view (click once on the YX window), press and hold the left mouse button. Now move your mouse a bit to the right and you will see a square with a dotted red line. This square is also called brush.

If you can't see the brush, then you can click onto the window where you want to see the brush and scroll up or down with your mouse wheel. Or you press and hold the right mouse button and
move the mouse around so that you will move the view in the window. If you want to resize a brush, press and hold the left mouse button somewhere outside of the square and move your mouse more to the left or to the right.
You'll see that the red box will grow or shrink. In the 3D view you can see your brush.

You can move around in the camera view by clicking on the window with the right mouse button (a grey cross appears) and pressing the arrow keys.
The angle of the view will change when you move the mouse. Of course this brush is only the floor of our first room since it is too low for walls. Press Esc for deselecting the brush. It should be black now in the top view (YX).
If you want to select it again, press shift and click on the brush. For the next brush go onto the YX window again and create one more smaller brush like I did:

For making a brush higher click on the ZY window (lower left), click and hold the left mouse button next to the brush and move your mouse vertically. It should now look like this:

As you can see the brush isn't on the same level as the other one.
For moving a brush, go with your cursor to the middle of the square, press your mouse button and again hold it. Now adjust the brush, so that it has the same height as the other one.

Select both brushes (press shift and click on them one after another) and stretch them into the width (ZX window)

Deselect both brushes now (Esc). As you can see we still need the wall on the opposite side. For this, you either create a new brush and adjust it, or you press Spacebar and copy the selected one. That's what we will do now.
Select the last wall brush and press Spacebar. We will get a new square which looks exactly the same like the one we've just selected:

Put it across from the first wall:

For the rest of the walls, create new brushes and adjust them:

Press Esc to deselect everything. For the ceiling select the floor and copy it. Click into the front view and put the brush onto the others:

Deselect all brushes. Afterwards press the right mouse button (everywhere, but NOT in the 3dview) and the entity menu pops up. All entries in there are entities. Go to info and click on info_player_deathmatch:

A pink box with an arrow will appear. The arrow goes into the direction the player will start. Place the box into the room and higher or lower it if it's not on the floor. It's important to mention,
that if you put it right in front of a wall or into a brush, the player won't be able to walk. Due to this always place the player start some units away from the wall or directly onto the floor:

If you want to change the direction of the player start, select it, press n to open up the entity attributes menu and press on the "180" button. These numbers fit to the top view (YX):

The arrow should have changed now:

Now we have to texture the room a bit so it looks shapelier. For texturing, select the brush you want to texture, go on textures and to "base". When you move your cursor over "base", a new window should appear including base_ceiling, base_wall etc:

Click on base_wall. Afterwards press t to open the "Texture Manager", scroll down until "atech1_f" and click on it.

Now all brushes you've selected before have this texture:

Deselect all brushes, press the right mouse button and click on "light":

A new window shows up and asks you to type in a value for the light intensity. Write 100 into the box and press Return:

When you've pressed Return you'll see a red circle around the light (blue square if you deselect it). Move the light until the outlined circle is in the room.

If you can't place it into your room, because the light radius is too high, press n, type in a lower value and press Return:

You've nearly finished your first room. We only have to compile it (convert from *.map into *.bsp) and start the map in Quake III Arena. To do this, click on "bsp" and then on the parameter in the picture:

A DOS window should appear now. This will need some time. It depends on the detail and structural brushes, caulked faces and size of the map, how long the compile needs. Now go into Q3A, open the console (^) and type in:/sv_pure 0/devmap name-of-your-map
If you did all things right, you will find yourself in the room you've just created:

Here you can get the map for this tutorial (place it into baseq3/maps):